Heatsink for a lamp



FIG. 1 is a perspective view of the new design for a heatsink for a lamp as seen from the side, top;

FIG. 2 is a front elevational view thereof, the rear view being the same;

FIG. 3 is a side elevational view thereof, the opposite side being the same;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines in the drawings depict portions of the heatsink for a lamp that form no part of the claimed design; the unshaded surface between the solid and broken line forms no part of the claimed design. 

CLAIM The ornamental design for a heatsink for a lamp, as shown and described. 